1. Field of the Invention
The present invention relates to a fastening element such as, e.g., a roof bolt, used primarily in mine and/or tunnel construction and including a cylindrical body having, in its end portion remote from an end facing in a setting direction, a longitudinal bore for receiving a mortar mass, and having, at its end facing in the setting direction at least one through-opening connecting the longitudinal bore with an outer surface of the body.
2. Description of the Prior Art
Fastening elements of the type described above are generally known. They function primarily for stabilizing walls of hollow spaces such tunnels, galleries and the like. They are used primarily for securing to each other following each other, in a direction transverse to the wall, the wall-forming strata. In many cases, the mechanical characteristics of the layers, which lie in immediate vicinity of the wall surface, in particular, their supporting resistance, changes as a result of formation of a hollow space. Therefore, these layers need be secured to further located, undamaged or unaffected layers or strata.
A fastening element or a roof bolt of the above-described type is disclosed, e.g., in U.S. Pat. No. 4, 055, 051. The U.S. Patent discloses a roof bolt that is formed of a tubular element provided, at one of its end, with a drilling head and, at its other opposite end, with load application means. The interior of the disclosed roof bolt is partially filled with mortar mass. An exit channel extends through the drilling head. The setting process of the disclosed roof bolt is effected in two steps. In the first step, the roof bolt forms, with the use of an available drilling tool, a bore in the constructional component, in particular, in the ground. The drilled-of and commutated stone, which is produced upon drilling with the drilling head of the roof bolt, is removed through outlet openings provided in the drilling head and the space between the bore wall and the outer surface of the fastening element. In a second step, a piston, which is provided at an end of the roof bolt facing in the direction opposite to the setting direction, is advanced in the setting direction, pressing out the mortar mass, which fills the interior of the roof bolt, through the openings provided in the drilling head.
A drawback of the disclosed roof bolt consists in that during the setting process, the mortar mass is first intermixed in the drilling head. With this, the quality of the intermixed mass depends on several factors such as, e.g., the rotational speed of the used drilling tool or constitution of the ground. If a mixing process is effected outside of the roof bolt, then additional tools and operational steps become necessary.
Accordingly, an object of the present invention is to provide a fastening element, such as, e.g., a roof bolt which would insure a good intermixing at any conditions.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing, in the setting direction, end region of the longitudinal bore of the fastening element, a mixing device located between through-opening means which connects the longitudinal bore of the fastening element with the wall of the fastening element, and the mortar mass.
Providing the mixing device inside of the fastening element permits to easily determine the mixing condition. When the mortar mass contacts the ground and the drillings, it is already intermixed. Therefore, even with critical mortar masses, a need in additional mixing device outside of the fastening element is eliminated. Furthermore, the design of the mixing device can be effected at small costs and taking into consideration the requirements the used mortar mass should meet. Placing the mixing device inside the fastening element, in the longitudinal bore, does not require any changes of the outer surface of the fastening element in comparison with the conventional fastening elements. Further, providing the mixing device between the trough-opening means and the mortar mass prevents exit of the non-mixed mortar mass into the bore formed in the constructional component.
Advantageously, the mixing device is located centrically in the longitudinal bore which insures an optimal intermixing of the mortar mass during the extrusion process.
The mixing device advantageously has a mixing channel formed as a static mixer. This proved to be beneficial to a cost-effective solution of the existing problem of achieving good intermixing of the mortar mass under any conditions prevailing outside of the fastening element. A need in the use of a dynamic mixing channel has been eliminated. However, under particular circumstances, a dynamic mixing channel can be used instead of the static channel.
Advantageously, the static channel or mixer is formed as a labyrinth-shaped channel connectable with the through-opening means through which the mortar mass is extruded. This type of the static channel finds particularly an application when one of the components of the mortar mass freely fills the longitudinal bore, without being contained in some enclosure. The labyrinth-shaped channel prevents extrusion of this component out of the fastening element before the start of the setting process. This channel can be closed, e.g., before the start of the setting process, by locking means releasable, e.g., under pressure. The locking means can be formed, e.g., by a pressure-sensitive foil.
Advantageously, the mixing device is located in the longitudinal bore with a possibility of a longitudinal displacement therealong. This insures an easy assembly of the fastening element. In addition, this displacement permits, if needed, to replace the mixing device to accommodate the specific requirement the used mortar mass has to meet.
The mixing device is preferably provided, at its end facing in the setting direction with a sealing piston. Thus, the mixing device includes an element which seals the longitudinal bore, in this case a sealing piston. In the unsetted condition of the fastening element, the sealing piston is located between the through-opening means, which connects the longitudinal bore with the outside of the fastening element, and the mixing device itself, thus closing the mixing channel. During the setting process, the applied pressure displaces the mixing device, together with the sealing piston, in the setting direction until the sealing piston or the mixing device hits a stop. The position of the stop is so selected that when the mixing device is stopped, the sealing piston does not block access to the through-opening means so that the mixing channel becomes operatively connected with the through-opening means, and the mortar mass can be extruded outside of the fastening element.
Advantageously, a collection space, connectable with the through-opening means, is provided between the sealing piston and the mixing device itself. The collection space is formed, e.g., by providing spacer means between the sealing piston and the mixing device and which keeps the sealing piston at a predetermined distance from the mixing device. The collection space is designed for collecting the intermixed mortar mass leaving the mixing channel of the mixing device, which mixing channel is connected with the collection space by an outlet opening. In the unsetted condition of the fastening element, the collection space is separated from the through-opening means by the sealing piston. During the setting process, the collection space becomes connected with the through-opening means, e.g., with the through-opening means becoming contiguous with the collection space. Naturally, the sealing piston itself can be provided with connection channels communicating with the through-opening means.
The mixing device is provided, at its end facing in a direction opposite the setting direction, with piercing means. This permits to pack the mortar mass for use with the fastening element in a bag. The piercing means can include a blade-like piercing element. Preferably, the piercing means should include sufficiently sharp element(s) for piercing the mortar mass-surrounding enclosure to provide for squeezing the mortar mass out of its enclosure.
Preferably, the cross-section of the mixing channel is smaller than the cross-section of the longitudinal bore in order to provide for an increased flow speed of the mortar mass through the mixing channel. This provides for better intermixing of the mortar mass.
Advantageously, the mixing device is formed of a mortar mass-resistant plastic material. Instead of a plastic material, other mortar mass-resistant materials can be used for forming the mixing device. In addition, the wall of the longitudinal bore which can, e.g., be made of metal, can have a plastic material coating for protecting the wall from the mortar mass or its component. Alternatively, a sleeve formed of a plastic material can be inserted in the longitudinal bore.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction its mode of operation, together with additional advantages and objects thereof, with be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.